Fix link to ReadTheDocs in Readme

Readme.md

@@ -1,7 +1,7 @@
 [![DOI](https://zenodo.org/badge/134823632.svg)](https://zenodo.org/badge/latestdoi/134823632)
 [![PyPI version](https://badge.fury.io/py/trixi.svg)](https://badge.fury.io/py/trixi)
 [![Build Status](https://img.shields.io/travis/MIC-DKFZ/trixi.svg)](https://travis-ci.org/MIC-DKFZ/trixi)
-[![Documentation Status](https://readthedocs.org/projects/trixi/badge/?version=latest)](https://trixi.readthedocs.io/en/latest/?badge=latest)
+[![Documentation Status](https://readthedocs.org/projects/trixi/badge/?version=develop)](https://trixi.readthedocs.io/en/develop/?badge=develop)
 [![Downloads](https://pepy.tech/badge/trixi)](https://pepy.tech/project/trixi)
 [![GitHub](https://img.shields.io/pypi/l/trixi.svg)](https://github.com/MIC-DKFZ/trixi/blob/master/LICENSE)
 <p align="center">
@@ -13,7 +13,7 @@ Finally get some structure into your machine learning experiments.
 
 * [Features](#features)
 * [Installation](#installation)
-* [Documentation](#documentation) ([trixi.rtfd.io](https://trixi.readthedocs.io/en/latest/))
+* [Documentation](#documentation) ([trixi.rtfd.io](https://trixi.readthedocs.io/en/develop/))
 * [Examples](#examples)
 
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